1. Field of the Invention
The present disclosure relates generally to the production of polystyrene and more specifically to the production of polystyrene having a broad molecular weight distribution.
2. Background of the Invention
Copolymers of monovinylidene aromatic compounds such as styrene, alpha-methylstyrene and ring-substituted styrene comprise some of the most widely used thermoplastic elastomers. For example, styrene copolymers can be useful for a range of applications including disposable medical products, food packaging, tubing and, point-of-purchase displays. Styrenic copolymers are block copolymers that comprise polystyrenic segments interconnected with a matrix comprising compounds such as polybutadiene or polyisoprene. The polystyrenic segments give hardness or rigidity to the copolymer while the interconnecting matrix provides softness or flexibility.
The molecular weight of a thermoplastic elastomer will generally dictate the resultant physical properties of the thermoplastic. As a rule, the higher the molecular weight, the higher mechanical properties (e.g., tensile, flexural, compressive strength) will be. However, processing of very high molecular weight thermoplastics is quite difficult. For example, the molecular weight (Mw) of commercial polystyrene is typically in the range of 200-350 kDa. This limits the physical properties but ensures good processibility. However, polymers having fractions of high and low molecular weight components would provide materials having both the desired strength (due to the high molecular weight components) and processability (due to the low molecular weight components). Thus a need exists for a styrenic copolymer having a good balance between strength and processability.